1. Field of the Invention
The present invention relates to an ejection condition determination method of determining an ejection condition of droplets by relatively moving a recording medium only once with respect to a recording head including a plurality of recording elements which eject the droplets in a transport direction crossing an arrangement direction of the plurality of recording elements, so as to form an image formed by a plurality of dots on the recording medium, and an image forming method and an image forming apparatus using the ejection condition determination method.
2. Description of the Related Art
In recent years, with the rapid progress of an ink jet technique, color and large size printing in which high speed and high image quality are compatible has been realized by an ink jet recording type image forming apparatus. In this recording type, droplets of a plurality of kinds of inks (for example, CMYK inks) are ejected onto a recording medium so as to form a plurality of dots, thereby obtaining a printed matter. This kind of apparatus is used for, particularly, a wide field in application to signs and display, and is also applicable to printing of, for example, a storefront point of purchase (POP), wall poster outdoor advertising, a signboard, and the like.
In addition, in this recording type, a single pass type of using a recording head (hereinafter, referred to as a line head) including a plurality of nozzles arranged in a predetermined direction has attracted special attention. This is because an image can be formed by moving a recording medium or a line head only once in a transport direction crossing the predetermined direction, and various specifications (high speed, low power consumption, and high image quality) required in application to signs and display can be all compatible.
Meanwhile, it is most preferable that ejection states of all the nozzles included in the line head be favorable at all times in order to stably obtain high quality printed matters. However, it is realistically very difficult to secure and maintain the above-described ejection states in all line heads in terms of productivity including processing accuracy, costs, and the like. Therefore, various image correction techniques for positively suppressing deterioration in image quality have been proposed on the premise that there may be a defective nozzle in the line head.
JP2011-201121A (Abstract, and FIGS. 3 and 17) has proposed a method and an apparatus in which a correction coefficient for non-ejection correction is determined in view of the fact that patterns of landing interference occurrence are different depending on relative positional relationships between respective nozzles. JP2011-201121A also describes a drawing example of a test chart which is a set of patches formed with various ejection conditions.
JP2006-076086A (claim 2 and FIG. 12) and JP2007-160748A (claim 1, paragraph [0069], and the like) have proposed a method and an apparatus in which density reduction due to non-ejection from a defective nozzle is compensated for using N (where N is an integer of 2 or more) nozzles around the defective nozzle. Particularly, JP2006-076086A (claim 2 and FIG. 12) specifically discloses addition and subtraction of a correction amount becoming smaller as the distance from the defective nozzle increases being repeated alternately for each pixel.